ENDS AND CONNECTIONS OF THE BUNDLES. 385 



(5) In the regions of attachment of Balanophora and Langsdorffia, according to 

 the authors mentioned, and the earUer investigations of Goppert ^, an additional phe- 

 nomenon occurs, which Ukewise belongs to this series. In these cases thick, variously 

 ramified vascular bundles, arising as branches from the wood of the host-root 

 attacked, grow into the parenchyma of the tuber of attachment, their branches 

 having broad blind ends in the parenchyma of the tuber. According to the existing 

 investigations, a direct connection between these excrescences and the parasites' own 

 bundles does not take place, or is at any rate doubtful. The bundles of the ex- 

 crescence are thick strands attaining more than i™in in thickness, and their branches 

 have broad ends, which may even be swollen in a club-like manner. They consist 

 of thick vascular masses, which are accompanied by delicate elongated elements re- 

 quiring further investigation ; they are penetrated by narrow divaricating bands of the 

 thin-walled parenchyma belonging to the parasite (cf. Graf Solms, /. c). 



Sect. 114. Conneclions 0/ Bundles. Where one vascular bundle-trunk branches 

 off from another, or, otherwise expressed, where it attaches itself to another, the 

 equivalent regions and elements of the two are in continuity. Where the arrange- 

 ment and orientation of the parts of the bundles in question are similar, as is the 

 case in most stems, and in the lamina of foliar expansions, the above fact indicates 

 the structure of the region of union in the most essential points ; various individual 

 differences follow from the general principle that the special structure of every 

 bundle may change in successive transverse sections. 



Where the arrangement of the parts and the orientation of the bundles is 

 different, torsions and displacements, both of the individual portions of the bundle, 

 and of any strands or sheaths that may accompany it, must take place towards and 

 at the place of union, in order to establish continuity of the equivalent elements ; and 

 with these torsions other changes of structure may be connected, besides those 

 relating to the orientation of the parts. 



Those cases of the union of bundles of unlike orientation which are remarkable in 

 these respects fall under two main categories, namely, connections between bundles 

 belonging to the same axis, and connections between the bundles of a main and a 

 lateral axis. 



I. Of the former category we have here first to mention the connection of 

 the bundle-system of the stem with the radial bundle of the main root in the typical 

 Dicotyledons and Gymnosperms^ The hypocotyledonary stem of these plants 

 contains, as described above, two or more separate, collateral bundles of normal 

 orientation, and towards the main root these approach one another so as to unite to 

 form its axial bundle. In the hypocotyledonary stem the primitive tracheae lie at the 

 inner edge, the phloem at the periphery of each bundle. In the axial bundle of the root 

 the primitive vessels occupy the outer edge of every xylem-plate, and the phloem- 

 bands alternate laterally with the xylem-bands. The investigation of the longitudinal 



' I.e. at p. 254. 



" Mettenius, Anat. d. Cycadeen, I.e. p. 602. — Dodel, DerUebergang des Dicotyledonen-Stengels 

 in die Pfahlwurzel, Pringsheim's Jahrb. Bd. VIII. — Strasburger, Die Coniferen irnd die Gnetaceen, 

 p. 360. — Van Tieghem, Canaux Secreteurs, /. e. — S. Goldsmith, ' Beitr. zur Entwickelungsgeschichte 

 d. Fibrovasalmassen im Stengel und in der Hauptwurzel der Dicotyledonen,' could not be made use 

 of for the present work. [Gerard, Recherches sur le passage de la racine a la tige, Ann. Sci. Nat. 

 6 ser. torn. Ii. 1881.] 



C C 



